1. Field of the Invention
This invention relates to tubing expansion, and in particular to an expansion tool and method for expanding tubing downhole.
2. Description of the Related Art
The oil and gas exploration and production industry is making increasing use of expandable tubing for use as, for example, casing and liner, in straddles, and as a support for expandable sand screens. The tubing may be slotted, such as the tubing and sand screens sold under the EST and ESS trade marks by the applicant, or may have a solid wall. Various forms of expansion tools have been utilised, including expansion cones and mandrels which are pushed or pulled through tubing by mechanical or hydraulic forces. However, these methods typically require transfer of significant forces from surface, and furthermore there are difficulties associated with use of hydraulic forces in the expansion of slotted tubing; the presence of the slots in the unexpanded tubing prevents the use of hydraulic force to drive the cone or mandrel through the tube. A number of the difficulties associated with expansion cones and mandrels may be avoided by use of rotary expansion tools, which feature radially extending rollers which are urged outwardly into rolling contact with the tubing to be expanded while the tool is rotated and advanced through the tubing. However, it has been found that the torques induced by such rotating tools may induce twisting in the expandable tubing, particularly in slotted tubing.
It is among the objectives of embodiments of the present invention to provide an expansion method and apparatus which obviates or mitigates these difficulties.